Mole ratios Transitional Reasoning Download PDF

Questions

1. 1.

   A fuel engineer analyzes the complete combustion of an unknown gaseous hydrocarbon, $\text{C}_x\text{H}_y$, in excess oxygen. Complete combustion of 1.5 mol of this hydrocarbon requires exactly 7.5 mol of $\text{O}_2(g)$ and produces $\text{CO}_2(g)$ and $\text{H}_2\text{O}(g)$ in a $3 : 4$ mole ratio. Based on these stoichiometric mole ratios, what is the molecular formula of the hydrocarbon?

   • A) $\text{C}_3\text{H}_8$
   • B) $\text{C}_2\text{H}_6$
   • C) $\text{C}_4\text{H}_{10}$
   • D) $\text{C}_3\text{H}_6$
2. 2.

   In a metallurgical extraction process, iron(III) oxide is reduced by carbon monoxide according to the balanced equation $\text{Fe}_2\text{O}_3(s) + 3\text{CO}(g) \rightarrow 2\text{Fe}(s) + 3\text{CO}_2(g)$. An industrial furnace is continuously supplied with a feed stream where the mole ratio of $\text{CO}(g)$ to $\text{Fe}_2\text{O}_3(s)$ is maintained at $5 : 1$. If $2.4\text{ mol}$ of $\text{Fe}_2\text{O}_3(s)$ is completely consumed, what is the mole ratio of unreacted $\text{CO}(g)$ to produced $\text{CO}_2(g)$ in the exhaust stream?

   • A) 2 : 3
   • B) 5 : 3
   • C) 3 : 2
   • D) 2 : 5
3. 3.

   An airbag safety system utilizes the sequential reactions $2\text{NaN}_3(s) \rightarrow 2\text{Na}(s) + 3\text{N}_2(g)$ and $10\text{Na}(s) + 2\text{KNO}_3(s) \rightarrow \text{K}_2\text{O}(s) + 5\text{Na}_2\text{O}(s) + \text{N}_2(g)$ to generate gas while neutralizing sodium metal. To completely consume all sodium produced in the first reaction and collect a combined total of 1.60 mol of $\text{N}_2(g)$ across both stages, what amount of $\text{NaN}_3(s)$ must react initially?

   • A) 1.00 mol
   • B) 1.07 mol
   • C) 0.80 mol
   • D) 1.60 mol
4. 4.

   To produce high-purity silicon for semiconductor manufacturing, silicon tetrachloride vapor is reduced with hydrogen gas according to the equation $\text{SiCl}_4(g) + 2\text{H}_2(g) \rightarrow \text{Si}(s) + 4\text{HCl}(g)$. An industrial reaction vessel is charged with 6.0 mol of $\text{SiCl}_4(g)$ and 10.0 mol of $\text{H}_2(g)$. Assuming the reaction proceeds until the limiting reactant is completely consumed, what is the total amount of gas remaining in the vessel?

   • A) 20.0 mol
   • B) 21.0 mol
   • C) 24.0 mol
   • D) 26.0 mol
5. 5.

   A chemist heats a mixture containing 0.80 mol of ammonia gas and an excess of solid copper(II) oxide according to the balanced equation $2\text{NH}_3(g) + 3\text{CuO}(s) \rightarrow 3\text{Cu}(s) + \text{N}_2(g) + 3\text{H}_2\text{O}(g)$. After the reaction stops, exactly 0.90 mol of solid copper is recovered from the vessel. Assuming no other reactions occur, how many moles of ammonia gas remain unreacted?

   • A) 0.20 mol
   • B) 0.30 mol
   • C) 0.60 mol
   • D) 0.50 mol